The present invention relates in general to the structural and functional combination of a fuel filter and a fuel-water separation unit. More specifically, the present invention relates to such a combination which includes an xe2x80x9cintegratedxe2x80x9d fuel pump with selected operational safeguards.
In the field of diesel engine technology, it is common to use fuel injection systems. Such fuel injection systems include small, closely toleranced apertures and clearances with precision machining and matching of cooperating components. The proper functioning of these components and of the fuel injection system generally depends, in part, on the fuel reaching these components being free of contaminants, at least of a magnitude which could affect performance. If the fuel is not adequately or properly filtered, the fuel injection system components are exposed to possible damage and subjected to premature wear. Other concerns with the delivery and use of fuel which is not adequately or properly filtered include inefficient combustion, high fuel consumption, poor starting, rough idle, and reduced engine power.
Many diesel engines use a transfer or fuel supply pump to aid in the delivery of fuel from the fuel tank, through the fuel filter and other components, to the inlet of a high-pressure gear pump such as a fuel-injection pump. The use of this transfer pump aids in priming of the fuel system, supplying pressurized fuel, and increases the useful life of the fuel filter. Very often the transfer pump is mounted in a remote location that then requires the use of extra hoses, connectors, clamps, etc. An integrated fuel filter and pump assembly designed to reduce the part count and simplify installation would be an improvement to such systems and would be of significant economic benefit to the OEM of the diesel engine.
Another consideration when a transfer pump is employed is the locating of this pump within the fuel flow path relative to the location of the fuel filter. When the transfer pump is downstream from the fuel filter, the fuel is actually pulled through the fuel filter by suction, as contrasted to a fluid pushing force directing the fluid through the filter when the transfer pump is located at a point which is upstream from the fuel filter. While the differences between an upstream location and a downstream location might seem inconsequential, they are not. There are substantial pressure and force differences because typically the maximum system vacuum level is between 5 and 7 psi and, with a fuel filter placed in the line, the allowable restriction across the suction side of the fuel filter could be limited, typically 1 to 3 psi. The available pushing force of a transfer pump located on the upstream side of the fuel filter is over 30 psi. The allowable restriction across the pressure side of the fuel filter could be over 5 psi.
It is desirable to have a higher rather than a lower pressure applied to the fuel filter. For example, if organic, heavy fuel droplets are present, it is preferable to push these droplets through the filter so that they can be burned during the combustion cycle. With a lower pressure system, these droplets are not pulled through the filter and thus build up on the filter element. The reduced flow which this causes shows a xe2x80x9cfalsexe2x80x9d or premature indication of filter plugging and may confuse the user into believing that it is time to replace the filter element. Another benefit of a higher input pressure to push the fuel through the filter rather than pulling or suctioning the fuel through the filter involves the creation of vapor bubbles. If the suctioning force (5 to 7 psi) is too high in view of the filter restriction (1 to 3 psi), vapor bubbles can be created in the fuel line. When these vapor bubbles are introduced into the fuel injection system, they result in inefficient engine operation and the result is lower power. The creation of an apparent low power condition may confuse the operator into believing that the fuel filter is restricted, causing shutdown and (premature) element replacement.
As should be understood, it would be an improvement to incorporate an upstream fuel transfer pump with a fuel filter so that the number of connection parts can be reduced and the benefit of using a high pressure pushing force realized. By configuring the housing of the integrated combination for mounting to an engine, packaging and servicing efficiencies result. By separately interfacing the filter element (or cartridge) and the fuel transfer pump with the remainder of the assembly, it is easy to change the filter cartridge without needing to disturb or disassemble the fuel transfer pump. A safety interlock as part of the present invention precludes the delivery of fuel, by disabling the fuel transfer pump, unless a filter cartridge is properly installed in the filter housing.
One desirable design feature of a fuel filter assembly is to configure the fuel filter assembly with a water separation capability. It is the design of the filtering element and the configuration of the fuel flow path which provides this water separation capability. The water which is separated is then collected in the vicinity of a drain opening (valve controlled) and due to density differences, the water stays below the fuel which is being processed by the filter. A water-in-fuel sensor indicates when the accumulated water is to be drained. Other desirable design features of a fuel filter assembly include configuring the fuel filter assembly with such items as a temperature sensor, a fuel heater, a diagnostic port, and a fuel strainer. A corresponding design challenge is to be able to incorporate all of these features and components, along with the fuel transfer pump, into a single assembly with a size and shape which is compatible with current diesel engine designs and with the current space allocations in such diesel engine designs for the fuel filter assembly. The present invention answers this design challenge in a novel and unobvious manner.
A fuel filter assembly for filtering a flow of fuel according to one embodiment of the present invention comprises an outer shell defining a hollow interior and, at a first end, a fuel inlet passageway, a fuel outlet passageway, and a water collection region, the outer shell having a second end which is open and constructed and arranged to be closed by receipt of a closing member, a fuel filter cartridge installed into the hollow interior, the fuel filter cartridge including a filter element which defines an interior space and which is constructed and arranged for water separation, a fuel transfer pump installed into the interior space and being operable to push fuel through the filter element, and a removable lid constructed and arranged for receipt by the outer shell for closing the second end.
One object of the present invention is to provide an improved fuel filter assembly which includes a fuel transfer pump and a water separation capability.
Related objects and advantages of the present invention will be apparent from the following description.